1. Field of the Invention
This invention relates to the field of expandable tubulars and more specifically to a tubular expansion apparatus having one anchor longitudinally moveable relative to another anchor.
2. Background of the Invention
In conventional drilling operations, it may be desirable to insert a tubular in a wellbore and expand the tubular downhole to make a casing repair, or in other applications to isolate an unconsolidated portion of a formation that is being drilled by expanding the tubular against the formation.
Various techniques to accomplish such tubular expansion have been attempted in the past. In one technique, an apparatus utilizing a casing packer as an anchor in combination with an expansion swage and a hydraulic cylinder allows radial expansion of long sections of the tubular. A drawback to such a technique having an apparatus with a single anchor positioned in the front of the swage is that the technique may not provide sufficient reaction force for the exit of the swage from the tubular at the end of the expansion process, which may result in the expansion process not being completed. Another conventional technique utilizes two anchors with one anchor in the front and the other anchor in the back of the swage. A drawback to this technique is that two anchors in such configuration may not allow for longitudinal shrinkage of the tubular upon its radial expansion, which may result in high longitudinal stresses and excessive wall thinning of the expanded tubular and may decrease burst and collapse resistance of the tubular.
Consequently, there is a need for an apparatus and technique for reliable and complete radial expansion of a tubular, which may allow for improved performance characteristics of the tubular compared to tubulars expanded by conventional techniques.